Metarhizium rileyi biopesticide to control Spodoptera frugiperda: Stability and insecticidal activity under glasshouse conditions.

The insect-pathogenic fungus Metarhizium rileyi is highly sensitive to nutritional and environmental conditions which makes it difficult to produce as a stable biopesticide. In this study, a Colombian isolate of this fungus was produced in bulk, and conidia were formulated as an emulsifiable concentrate (EC). The stability of formulated conidia was studied. Conidial viability was maintained at >85 % viability for 12 m under refrigeration and for >three months at 18 °C. The pH values were stable, while contaminant content was significantly reduced. The efficacy of the EC to control Spodoptera frugiperda (Smith) was correlated with the storage time using different mathematical models, and conservative values of six and 12 months at 8 °C and 18 °C respectively, were established. Finally, the EC was evaluated in maize plants under glasshouse conditions. The LC50 and LC90 were estimated to be 1.17 × 104 and 4.03 × 106 conidia/mL respectively and a 57 % reduction in recent damage of plants was achieved. This study demonstrated the potential of M. rileyi formulated as EC to control S. frugiperda in maize. Therefore, it is necessary to continue developing this biopesticide, in order to deliver a new tool to be integrated in pest management programs.